1. Field of the Invention
The present invention relates to a method and apparatus for cutting a continuous corrugated member, for example, a louver-forming corrugated fin for a heat exchanger, for example, an automobile radiator.
2. Description of the Prior Art
Recently, it has been desired to reduce the weight and manufacturing cost of heat exchangers, such as automobile radiators. For this purpose, various attempts have been made to increase the heat radiation per unit weight of heat exchangers. In one method, the width of the corrugated fin used for the radiator core is narrowed, the pitch or distance between adjacent crest portions on one side face of the corrugated fin is reduced, and the number of crest portion is correspondingly increased. There has already been proposed a corrugated fin with a width 1/2, a pitch about 1/2, and a number of crest portions about two times that of conventional corrugated fins.
The process for the preparation of corrugated fins ordinarily comprises the steps of forming a thin strip member into a continuous corrugated member, contracting the pitch of the corrugated member, and cutting the corrugated member into sections having a predetermined number of crest portions.
The latter two steps may be reversed, i.e., the corrugated member may be cut before the contraction or cut after the contraction.
In cutting before contraction, a thin strip member is formed by rollers into a continuous corrugated member having a crest pitch larger than that of a final product. The continuous corrugated member is then conveyed in a longitudinal direction thereof and cut into sections having a predetermined number of crest portions by a cutting device. The pitch of the corrugated member is then contracted by a contracting device.
In cutting after contraction, a thin strip member is formed by rollers into a continuous corrugated member having a crest pitch larger than that of a final product. The corrugated member is then conveyed in a longitudinal direction thereof and contracted to a predetermined crest pitch by a contracting device. The corrugated member is then cut into sections having a predetermined length by a cutter device.
Conventional methods for cutting a continuous corrugated member include scissors cutting and punch cutting. In scissors cutting, a stationary cutter and a moving cutter, each having a relatively large thickness, are used together to cut the corrugated member. Scissors cutting is suitable for cutting a corrugated member having a large pitch and is mainly adopted for cutting before contraction. In punch cutting, a thin moving cutter is inserted into a slit formed on one end of a stationary cutter. Punch cutting is suitable for cutting a corrugated member having a small pitch and is mainly adopted for cutting after contraction.
In conventional cutting before contraction with scissors cutting, the corrugated member can be cut irrespective of the pitch of the final product. However, since the cut end of the corrugated member has to be introduced between a pair of feed rollers after the corrugated member has been cut, the feed of the corrugated member into the space between the rollers becomes unreliable upon an increased speed of manufacturing the corrugated fin, i.e., speed of conveying crest portions of the corrugated member per unit time.
In conventional cutting after contraction with punch cutting, since louvers are usually simultaneously formed on the continuous corrugated member, it is necessary to insert the moving cutter between the louvers of the corrugated member. However, when the cutter inserted to cut a corrugated member having a narrow pitch width, for example, a crest pitch corresponding to 1/2 of the pitch of a conventional corrugated fin, the gap between the two louvers of the corrugated member is smaller than the thickness of an ordinary moving cutter. Therefore, when trying to insert the moving cutter between the two louvers, the louvers are caught on the cutting edge portion of the moving cutter and the corrugated member is crushed. If the thickness of the moving cutter is reduced, the resultant moving cutter becomes subject to vibration and is reduced in strength.
Moreover, in conventional cutting after contraction, the position of the cutting device with respect to the conveying direction of the corrugated member is fixed and that fixed cutting device cuts the corrugated member while the member is moving. Therefore, the moving cutter must complete its descent and ascent during the passage of one crest portion of the corrugated member. Conversely, the conveying speed of the corrugated member is limited by the speed of the descent and ascent of the moving cutter. In practice, the conveying speed is thus limited to about 4000 crest portions per minute. Therefore, when it is intended to obtain a corrugated fin having a crest pitch corresponding to about 1/2 of the pitch of a conventional corrugated fin, it takes twice as long to form one corrugated fin as with a conventional corrugated fin. This means productivity drastically reduced of the corrugated fins and increased manufacturing cost.